1. Field of the Invention
The present invention relates to a ratchet wrench.
2. Background of the Invention
According to a conventional ratchet wrench, power generated by an air motor (i.e., a motor driven by compressed air) is transmitted to a ratchet mechanism via a reduction gear mechanism, to thereby rotate a tightening member connected to the ratchet mechanism.
When the tightening torque of such a conventional ratchet wrench is to be increased, the following two methods have been employed:
a) increasing the longitudinal size of the air motor; and PA0 b) increasing the outer diameter of the rotor of the air motor.
However, method a) has a drawback in that, even when the motor output is increased by increasing the longitudinal size of the air motor, the tightening torque does not necessarily increase. Method b) has a drawback in that there is a limit to how much the outer diameter of the rotor can be increased; that is, since the motor housing serves as a grip of the ratchet wrench and the grip cannot be made extremely large in diameter, the outer diameter of the rotor of the air motor cannot be enlarged very much.